The invention relates to a method for fabricating concrete blocks or concrete slabs of various formats and sizes, in which concrete is charged into molds for a plurality of blocks or slabs, its surface layer or its face concrete layer exhibits a ground color and its surfaces contain diversely colored places, the concrete is compacted by vibration and/or tamping and then cures. It is common to charge the raw concrete for concrete blocks and concrete slabs into the molds first, then to charge the face concrete, and then to compact the concrete blocks or concrete slabs. It is also possible, however, to fabricate the concrete blocks or concrete slabs in a single-step method without face concrete. Here, in order to fabricate varicolored concrete blocks or concrete slabs, it is known to impart a ground color to the surface layer in the single-step method or to the face concrete layer, as desired, which ground color can correspond to the concrete color without pigmentation or is pigmented in various colors.
From EP-1 017 554 B1 it is further known to fabricate the concrete mortar forming the face layer by variously pigmented layers, which are held one above another in the supply vessel and move freely downward in the supply vessel, thus mixing and passing onto the coarse concrete, guided via baffles, in order to form a marbled face layer that is subsequently compacted. This is a serviceable method wherein, however, there arise varicolored marbled batches that are capable to only a limited degree of satisfying the visual requirements for concrete blocks or concrete slabs that are supposed to look similar to natural stones, because only dot-like color patterns arise.